Present development of fast, cheap and miniaturized electronics and sensory devices opens new pathways for the development of sophisticated equipment to overcome limitations of the human senses. Humans rely heavily on vision to sense the environment in order to achieve a wide variety of goals. However, visual sensing is generally available only for a limited visible range of wavelengths, roughly 400 nm (nanometers) to 720 nm, which is a small fraction of the range of wavelengths (180 nm through about 10,000 nm) at which interesting physical effects and/or chemical effects occur. Audible sensing, over an estimated audible range of 200 Hz (Hertz)-20,000 Hz, is similarly limited, but this range is a larger fraction of the audibly interesting range 10 Hz-105 Hz). Further, use of binaural hearing to provide audible clues as to depth and relative location is generally better developed than are the corresponding mechanisms associated with formation of visible images.
Since the time of Aristotle (384-322 BC), humans have been interested in perceiving what is beyond normal “vision”. Roentgen's discovery of X-Rays enabled him to see inside living tissue, and “vision” was thereby extended beyond the naked eye. In the following years, imaging and sensing techniques have developed so rapidly that astronomy, medicine and geology are just few of the areas where sensing beyond the normal visual spectrum has been found useful. Altering and extending human “vision” changes our perception of the world
According to some recent research in evolution of the sight system for animals, reported in “What Birds See” by Timothy H. Goldsmith, Scientific American, July 2006, pp. 68-75, certain bird species have a tetra-chromatic color sensing system, with color bands spanning the near-ultraviolet, violet, green and red wavelengths, in contrast to the tri-chromatic (for primates, humns and some birds) or bi-chromatic (for other animals) color sensing systems that cover only two or three visible wavelength bands. The tetra-chromatic color sensing system of the birds allows more subtle sensing of color differences, much as HD radio claims to allow receipt of radio frequencies between the 0.2 kHz signposts of conventional commercial radio. This extra color sensing subtlety available to some birds is not available, and is not likely to become available, generally to humans and/or primates.
Further, the human audible sensing system is capable of learning to process and interpret extremely complicated and rapidly changing auditory patterns, such as speech or music in a noisy environment. The available effective bandwidth, on the order of 20 kHz, may support a channel capacity of several thousand bits per second. The known capabilities of the human hearing system to learn and understand complicated auditory patterns provide a basic motivation for developing a visual image-to-sound mapping system.
What is needed is a system that converts “visual signals”, defined herein as signals with at least one associated wavelength in the ultraviolet, the visible and/or the infrared, to one or more audibly perceptible signals with associated audio parameters that can be recognized and distinguished by the human ear. Preferably, these signals should include an audible indication of change, or change rate with time, of one or more visual image parameters. Preferably, these audio signals should provide monaural and/or binaural signaling that is analogous to depth clues and/or distance clues provided by visually perceptible images. Preferably, the audible signal parameters should have an intuitive connection with the visual signal parameters to which the audible signal parameters correspond.